A method and an arrangement are provided for maintaining the oxidation of NO to NO2 in an oxidation catalytic converter arranged in a vehicle, the vehicle including an internal combustion engine which in operation emits exhaust gases to an exhaust gas after treatment system including the oxidation catalytic converter. A predetermined quantity of hydrocarbon is delivered to the exhaust gas aftertreatment system or the engine over at least one predetermined time interval for the purpose of maintaining the working temperature or regenerating an exhaust gas aftertreatment unit. The quantity of hydrocarbon is delivered to the exhaust gas aftertreatment system or to the engine through an injection with at least one predetermined fragmentation frequency and an injection period in order to maintain an NO2 production in the exhaust gas aftertreatment system that prevailed immediately prior to said time interval for the hydrocarbon injection.